1. Field of the Invention
The present general inventive concept relates to a front surround sound reproduction system using an array of speakers, and more particularly, to a front surround reproduction system to improve a stereo effect of mid and low frequency signals by using a psychoacoustic model and a method thereof.
2. Description of the Related Art
A conventional front surround sound reproduction system employs a sound projector technology that provides a stereo effect using an array of front speakers without side and back speakers.
That is, by using the speaker array, the front surround sound reproduction system forms a sound beam from a surround channel signal, and projects the sound beam onto a wall so that sound reflected from the wall reaches a listener.
Accordingly, the listener feels a surround sound stereo effect as if the sound comes from side and back speakers, due to the reflected sound.
However, though a high frequency signal is formed as a sound beam, mid and low frequency signals are not formed as sound beams due to physical constraints and therefore are reproduced as the original signals through the front speaker array.
Accordingly, the front surround signal reproduction system cannot generate a stereo surround sound comparable to a sound signal of a home theater system using side and back speakers.
Accordingly, a variety of technologies have been introduced to solve the problem of how the conventional front surround reproduction system cannot easily generate a beam from mid and low frequency signals.
A technology related to this front surround reproduction system is disclosed in WO 04/075601 filed on Sep. 2, 2004, entitled “Sound Beam Loudspeaker System.”
FIG. 1A is block diagram of a conventional front surround sound reproduction system.
A multi-channel audio signal is decoded into a left channel signal (L), a right channel signal (R), a center channel signal (C), a surround channel signal, and a low frequency effect channel signal (LFE).
The decoded signals are input to a crossover system 410, and gains of the decoded signals are adjusted appropriately by a gain adjustment unit 411. Accordingly, a high pass filter 412 and a low pass filter 413 separate n surround channel signals and L, R, and C channel signals into a high frequency band and a mid and low frequency band, respectively. The separated high frequency signal is provided to an array of speakers to perform beam forming. The mid and low frequency signals are added to the low frequency effect channel and provided to a woofer to reproduce a low frequency band.
However, although the conventional technology illustrated in FIG. 1A improves the performance of high frequency beam forming, it degrades a surround sound stereo effect because mid and low frequency band signals are not beam-formed. Also, the conventional front surround sound reproduction system cannot experience the surround sound stereo effect in a listening space having one side open without a wall as illustrated in FIG. 1B, because a reflection of a high frequency signal by a wall rarely exists.